Tiengesellschaft



Feb. 3, 1931. F. J. FISCHER 1,790,981

CURRENT TRANSFORMER HAVING FIELD EQUALIZING CONDUCTING COATINGS Filed May 21, 1929 Aff Patent ed Feb. 3, 1931 UNITED STATES PATENT OFFICE- I'RANZ JOSEPH FISCHER, F DRESDEN, GER-MANY, ASSIGNOR T0 KOCH &'STEBZEL, AK-

. TIENGESELLSCHAFT, OF DRESDEN, GERMANY CURRENT TRANSFORMER HAVING FIELD-EQUALIZING CONDUCTING COATINGS Application filed May 21, 1929, Serial No. 364,818, and in Germany May 21, 1928. Y

My invention relates to current transform ers in which on the inside or on the outside of a leading-in insulator which contains the primary wmding of the transformer, conducting coatings are arranged for equalizing the electric field which extend along the inner or outer surface of the leadin -in insulator.

More particularly my inventlon relates to measuring current transformers the leadingin insulator of which is provided with a tun- .nel supporting the secondary winding and receiving the iron core on which the winding is came It is an object of my invention to improve an insulator of this type, and to this end I arrange on the insulator a conducting surface in the shape of a conducting coating on the wall, or on part of the wall, of an insulator which coatin is arranged intermediate the primary. win ing and a grounded art of the transformer,'wh1ch part may be a ange supv porting the insulator, a casing surrounding the transformer, the iron core of the transformer, or a se arate grounded coating. The

coating is insu ated from the primary winding and from the grounded part and, with the grounded art, constitutes a measuring condenser to w ich electrostatic instruments mag be connected.

ccording to my invention I arrange the coating in insulatedrelation to the usual conducting layers for equalizing the field. By thus insulating the coating, the equalizin coatings rotect the insulated coating, whic will be referred to hereinafter as the measurin coating, against disturbance by the electric field, and I thus obtainby very simple expedients an instrument which is a current and a voltage transformer adapted to be connected with electrostatic instruments.

In an embodiment of my invention to which, however, Ido not desireto be limited, the dielectric of the measuring condenser is constituted by a liquid, plastic or granular body with whlch the casing of the transform er is filled. The dielectric may be the same 1v11'ltl(1i which the cavity of the insulator is In adapting my invention to aset of en rimposed current transformers with eir primary windings connected in series, as descrlbed in my copending a plication for patent of the United States erial No. 282,922,

I may provide with a measuring coating only that'transformer, the flange or casing of which is grounded, or I may provide each transformer with a measuring coating so that it is possible to selectively ground any casing or flange of the unit and to utilize the measuring coating allotted to this flange. If the measuring coating is arranged on a wall of the insulator, it may be applied by 1 any known process, preferably by spraying. Preferably the measuring coating is made thicker than the equ'alizin coatings. I prefer producing a coating 0 such thickness as combination with transversely perforated insulators and embodying my invention are illustrated diagrammatically by way of example. I

In the drawings Fig. 1 is apartly sectional elevation of a I transversely perforated leading-in insulator, Fig. 2 is a section of the insulator showing a current transformer in position therein,

Fig. 3 is a sectional elevation of a potshaped current transformer, Fig. 4 is a sectional elevation of a otshaped transformer with-a bottle-shape insulator as described in my copending appli-' cation aforesaid, and

Fig. 5 is a sectional elevation of a graded transformer having several insulators, each with a transformer unit, as also described in the said copending apiplication.

Referring now to t e drawings, and first to Figs. 1 and 2, 11 is an insulator, 12 is a transverse erforation or tunnel in the insulator.

.14 is t e wall of the tunnel, 17 is the wall of the insulator, 20 are measuring coatings which are applied to the wall of the tunnel 12 on the inside and to the adjacent wall 17 of the insulator on the outside, and 21 and 22 are the usual coatings-for equalizing the electric field which are arranged in insulated relation to the measuring coatings 20, 20 so that there is no conducting connection between the measuring coatings 20 and the e ualizing coatings 21, 22. 13 is the'primary o the current transformer which surrounds the wall 14 of the tunnel 12, 15 is the secondary of the transformer, 16 is an iron core in the tunnel 12 on which the secondary 15 is wound, 18 is a grounded flange surrounding the insulator in the region of the metal coatings, and 19 arethe yokes of the corewhich are arranged to surround the outer perimeter of the insulator 11 and are held by the flange 18 which also supports the insulator itself. It-will appear from Fig. 2 that each measuring coating 20 is arranged'in insulated relationbetween the primary 13 on the one hand and the grounded flange 1-8andyokes 19 and core 16 which are parts of the current trans; former, on the other hand.

The measuring coatings may be applied according to any suitable method, for instance, by spraying, as mentioned above,-and may be connected with any suitable instruments such as voltmeters, synchronizing apparatus, indicators of excess voltage, wattmeters, and the like. Preferably the measuring coatings are made thicker than the directly connected to them, for instance, by

soldering after the strands of such conductors have been spread to the shape of a fan.

. Referring now to Fig. 3, 23 is a bottleshaped insulator open at the bottom and-provided with-a tunnel for the reception of the secondary 15 and its core 16, the primary 13 being wound about the tunnel, as described with reference to Fig. 2, the open bottom of ing 20 which in this case forms the bottom of the .bottle. 24 is an insulating filling in'the insulator, such as oil, quartz, sand and thelike. '26 is the grounded vessel of the transf former, 34 is one of the voltage terminals of th transformer and 33 is a conductor extending from the terminal 34 to the measuring -coating. 20 towhich it is securedb spreading and soldering its strands "as escribed. 28 is the usual equalizing coating. The measuring coating 20 is insulated from the primary 13. and from the the insulating. filling-24.

Referring now to 4, the insulator 27 is closed at the bottom below the tunnel 12,

' nwhich are arranged the seconda 1'5 and its core 16, as described, withthe primary 13 surrounding the tunneL' The measur' coatmg 20 is applied to the bottom of t e insulator, insulated from the equalizing coating 28 and connected with the terminal 34 by the conductor 33.

In Fig. 5 an insulator 2,7 as illustrated in Fig. 4 is inserted in the upper end of a second I insulator 29, each insulatorhaving the tunnel equalizing coatings so that conductors may be the insulator is closed by the measuring coatgrounded vessel 26 by referred to, and each containing a transformer unit, the tvvo units making up a graded transformer, as mentioned in the introduction. The upper insulator 27 with its transformer unit is designed exactly as described with reference to Fig. 4; The lower insulator 29 is provided with a suitable seat for the upper insulator at its upper end and equipped with the other transformer unit comprising the primary 13", the secondary 15' and the iron core 16', the wound about the wall 14' of the tunnel in the lower insulator-29, and the secondary with its core being inserted in the tunnel. The measuring coating 20' is arranged at the bottom of the lower transformer 29 which is equipped with 'the usual equalizing coatings 28 at the sides of the measuring coating 20. The coating 20 is connected with a voltage terminal 34 by a conductor 33, similarly as described with reference to 'Fig. 4.

If it is not desired 'to ground the casing 30', but the flange 18 of the upper insulator 27, an insulating coating 31 is secured to the measuring coating 20, and a second measuring coating 32 is secured to the insulating coating 3'1, this second coating 32 being grounded by a conductor 33" 'is that the ratio of capacities is independent of the insulating filling 24.

In any of the'cases described with reference which is se 'cured to the flange "18 of the upper transwhile the coating 20 is connected primary being to Figs. 3-5 the measuring coating may be igs arranged as described with reference to 1 and 2, that is, wall 14 and on wall 17.

I wish it to be understood that desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled 'in the art.

In the claims aifixed to this specification no selection of any particular modification of the invention is intended to the exclusion of'other modifications thereof and the right to subsequently make claim to any modification not covered by these claims isexpressly reserved.

I claim 1. In a currenttransforiner a leading-in insulator, 'a primary winding in said inon the inside of the tunnel the outside of the insulator outer wall of .said insulator, a conducting coating on the inner wall of said tunnel and on the adjacent outer wall of said insulator,

which coating is insulated fromall other parts, and a terminal electrically connected with said conducting coating.

I do not 2. Ina current transformer a leading-in insulator which is open at the base, a primary winding in said insulator, a conducting casing having a bottom surrounding the lower part of said insulator, field-equalizing coatings on the outer surface of said insulator, a conducting coating fitted into the opening at the base of said insulator so as to close it, and insulated from all other parts, and a terminal electrically connected with said conducting coating.

3. In a current transformer a leading-in insulator which is open at the base, a primary winding in said insulator. a. conducting casing having a bottom surrounding the lower part of said insulator, a dielectric filling between said casing and said insulator, fieldequalizing coatings on the outer surface of said insulator, a conducting coating fitted into the opening at the base of said insulator so as toclose it, and insulated from all other parts, and a terminal electrically connected with said conducting coating.

4. In a current transformer a leading-in insulator with insulating walls and insulating bottom, a primary winding in said insulator, a casing surrounding said insulator and having a conducting wall'an'd a conducting bottom, field-equalizing coatings on the outer surface of said insulator, aconducting coating on the outside of the bottom of said insulator opposite the bottom of said casing, and insulatedfrom all other parts, and a terminal electrically connected with said con ducting coating.

5. In a current transformer a leading-in insulator with insulatin walls and insulating bottom, a primary win ing in said insulator, a casing surrounding said insulator and having a conducting wall and a conducting bottom, a dielectric fillin between said casing and said insulator, fie d-equalizing coatings on the outer surface of said insulator, a conducting coatin on the outer surface of the bottom of said insulator oppositethe bottom of said casing, and insulated from all other parts, and a terminal electrically connected with said conducting coating.

6. In a current transformer a leading-in insulator with insulating walls and insulating bottom, a primary winding in said insulator,

coating, said coating being so thick as to permit soldering a conductor thereto.

8. A leading-in insulator havin a conducting coating on the outer wal of said insulator and adapted to constitute a measuring condenser in combination with another coating, said coating being so thick as to permit soldering a conductor thereto, and a stranded conductor having its strand spread in the manner of a fan and soldered to said coating.

9. In a current transformer a leading-in insulator, a primary winding in said insulator, grounded parts surroundin said insulator, metallic coatings electrical y insulated from each other on the outer surface of said insulator, one coating serving as field-equalizing coating and the other coating being arranged between and insulated from said primary winding and said grounded parts, and constituting a measuring condenser together with one of said grounded parts.

In testimony whereof I afiizi my si nature.

FRANZ JOSEPH FISG ER.

grounded parts secured to said insulator,

field equalizing coatings on the outer wall; of said insulator, a conducting coating on the outersurface of the bottom of said insulator which is insulated from all other parts, a dielectric on said coating, another conducting coating on said dielectric connected with a grounded part, and a terminal electrically connected with said conducting coat- I. A leading-in inusulator havin a con ducting coating on the outer wall 0 said insulator and adapted to constitute a measuring condenser in combination with another 

